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man:renameat

RENAME(2) Linux Programmer's Manual RENAME(2)

NAME

     rename, renameat, renameat2 - change the name or location of a file

SYNOPSIS

     #include <stdio.h>
     int rename(const char *oldpath, const char *newpath);
     #include <fcntl.h>           /* Definition of AT_* constants */
     #include <stdio.h>
     int renameat(int olddirfd, const char *oldpath,
                  int newdirfd, const char *newpath);
     int renameat2(int olddirfd, const char *oldpath,
                   int newdirfd, const char *newpath, unsigned int flags);
     Note: There is no glibc wrapper for renameat2(); see NOTES.
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     renameat():
         Since glibc 2.10:
             _POSIX_C_SOURCE >= 200809L
         Before glibc 2.10:
             _ATFILE_SOURCE

DESCRIPTION

     rename()  renames  a  file,  moving it between directories if required.
     Any other hard links to the file (as created using link(2))  are  unaf-
     fected.  Open file descriptors for oldpath are also unaffected.
     Various restrictions determine whether or not the rename operation suc-
     ceeds: see ERRORS below.
     If newpath already exists, it will  be  atomically  replaced,  so  that
     there is no point at which another process attempting to access newpath
     will find it missing.  However, there will  probably  be  a  window  in
     which both oldpath and newpath refer to the file being renamed.
     If  oldpath  and  newpath are existing hard links referring to the same
     file, then rename() does nothing, and returns a success status.
     If newpath exists but the operation fails  for  some  reason,  rename()
     guarantees to leave an instance of newpath in place.
     oldpath can specify a directory.  In this case, newpath must either not
     exist, or it must specify an empty directory.
     If oldpath refers to a symbolic link, the link is renamed;  if  newpath
     refers to a symbolic link, the link will be overwritten.
 renameat()
     The  renameat()  system  call  operates  in  exactly  the  same  way as
     rename(), except for the differences described here.
     If the pathname given in oldpath is relative, then  it  is  interpreted
     relative  to  the directory referred to by the file descriptor olddirfd
     (rather than relative to the current working directory of  the  calling
     process, as is done by rename() for a relative pathname).
     If oldpath is relative and olddirfd is the special value AT_FDCWD, then
     oldpath is interpreted relative to the current working directory of the
     calling process (like rename()).
     If oldpath is absolute, then olddirfd is ignored.
     The interpretation of newpath is as for oldpath, except that a relative
     pathname is interpreted relative to the directory referred  to  by  the
     file descriptor newdirfd.
     See openat(2) for an explanation of the need for renameat().
 renameat2()
     renameat2()  has an additional flags argument.  A renameat2() call with
     a zero flags argument is equivalent to renameat().
     The flags argument is a bit mask consisting of zero or more of the fol-
     lowing flags:
     RENAME_EXCHANGE
            Atomically  exchange  oldpath  and newpath.  Both pathnames must
            exist but may be of different types (e.g., one could be  a  non-
            empty directory and the other a symbolic link).
     RENAME_NOREPLACE
            Don't  overwrite newpath of the rename.  Return an error if new-
            path already exists.
            RENAME_NOREPLACE    can't    be    employed    together     with
            RENAME_EXCHANGE.
     RENAME_WHITEOUT (since Linux 3.18)
            This  operation  makes  sense  only for overlay/union filesystem
            implementations.
            Specifying RENAME_WHITEOUT creates a "whiteout"  object  at  the
            source  of the rename at the same time as performing the rename.
            The whole operation is atomic, so that if  the  rename  succeeds
            then the whiteout will also have been created.
            A   "whiteout"   is  an  object  that  has  special  meaning  in
            union/overlay filesystem constructs.  In these constructs,  mul-
            tiple  layers  exist  and  only the top one is ever modified.  A
            whiteout on an upper layer will effectively hide a matching file
            in  the  lower  layer,  making  it  appear as if the file didn't
            exist.
            When a file that exists on the lower layer is renamed, the  file
            is  first copied up (if not already on the upper layer) and then
            renamed on the upper, read-write layer.  At the same  time,  the
            source file needs to be "whiteouted" (so that the version of the
            source file in the lower  layer  is  rendered  invisible).   The
            whole operation needs to be done atomically.
            When  not  part  of  a  union/overlay, the whiteout appears as a
            character device with a {0,0} device number.
            RENAME_WHITEOUT requires  the  same  privileges  as  creating  a
            device node (i.e., the CAP_MKNOD capability).
            RENAME_WHITEOUT can't be employed together with RENAME_EXCHANGE.
            RENAME_WHITEOUT requires support from the underlying filesystem.
            Among the filesystems that provide that support are shmem (since
            Linux 3.18), ext4 (since Linux 3.18), and XFS (since Linux 4.1).

RETURN VALUE

     On  success,  zero is returned.  On error, -1 is returned, and errno is
     set appropriately.

ERRORS

     EACCES Write permission is denied for the directory containing  oldpath
            or  newpath,  or,  search  permission  is  denied for one of the
            directories in the path prefix of oldpath or newpath, or oldpath
            is  a  directory  and does not allow write permission (needed to
            update the ..  entry).  (See also path_resolution(7).)
     EBUSY  The rename fails because oldpath or newpath is a directory  that
            is in use by some process (perhaps as current working directory,
            or as root directory, or because it was open for reading) or  is
            in  use  by  the  system (for example as mount point), while the
            system considers this an error.  (Note that there is no require-
            ment  to return EBUSY in such cases--there is nothing wrong with
            doing the rename anyway--but it is allowed to  return  EBUSY  if
            the system cannot otherwise handle such situations.)
     EDQUOT The  user's  quota  of  disk  blocks  on the filesystem has been
            exhausted.
     EFAULT oldpath or newpath points outside your accessible address space.
     EINVAL The  new  pathname  contained a path prefix of the old, or, more
            generally, an attempt was made to make a directory  a  subdirec-
            tory of itself.
     EISDIR newpath  is  an  existing directory, but oldpath is not a direc-
            tory.
     ELOOP  Too many symbolic links were encountered in resolving oldpath or
            newpath.
     EMLINK oldpath already has the maximum number of links to it, or it was
            a directory and the directory containing newpath has the maximum
            number of links.
     ENAMETOOLONG
            oldpath or newpath was too long.
     ENOENT The link named by oldpath does not exist; or, a directory compo-
            nent in newpath does not exist; or, oldpath  or  newpath  is  an
            empty string.
     ENOMEM Insufficient kernel memory was available.
     ENOSPC The device containing the file has no room for the new directory
            entry.
     ENOTDIR
            A component used as a directory in oldpath or newpath is not, in
            fact,  a  directory.   Or,  oldpath  is a directory, and newpath
            exists but is not a directory.
     ENOTEMPTY or EEXIST
            newpath is a nonempty directory, that is, contains entries other
            than "." and "..".
     EPERM or EACCES
            The  directory  containing  oldpath has the sticky bit (S_ISVTX)
            set and the process's effective user ID is neither the  user  ID
            of  the  file to be deleted nor that of the directory containing
            it, and the process is not privileged (Linux: does not have  the
            CAP_FOWNER  capability);  or newpath is an existing file and the
            directory containing it has the sticky bit set and the process's
            effective  user  ID  is  neither  the  user ID of the file to be
            replaced nor that  of  the  directory  containing  it,  and  the
            process  is  not privileged (Linux: does not have the CAP_FOWNER
            capability); or the filesystem containing pathname does not sup-
            port renaming of the type requested.
     EROFS  The file is on a read-only filesystem.
     EXDEV  oldpath  and  newpath  are  not  on the same mounted filesystem.
            (Linux permits a filesystem to be mounted  at  multiple  points,
            but  rename()  does not work across different mount points, even
            if the same filesystem is mounted on both.)
     The  following  additional  errors  can  occur   for   renameat()   and
     renameat2():
     EBADF  olddirfd or newdirfd is not a valid file descriptor.
     ENOTDIR
            oldpath  is relative and olddirfd is a file descriptor referring
            to a file other than a directory; or  similar  for  newpath  and
            newdirfd
     The following additional errors can occur for renameat2():
     EEXIST flags contains RENAME_NOREPLACE and newpath already exists.
     EINVAL An invalid flag was specified in flags.
     EINVAL Both  RENAME_NOREPLACE  and  RENAME_EXCHANGE  were  specified in
            flags.
     EINVAL Both  RENAME_WHITEOUT  and  RENAME_EXCHANGE  were  specified  in
            flags.
     EINVAL The filesystem does not support one of the flags in flags.
     ENOENT flags contains RENAME_EXCHANGE and newpath does not exist.
     EPERM  RENAME_WHITEOUT  was specified in flags, but the caller does not
            have the CAP_MKNOD capability.

VERSIONS

     renameat() was added to Linux in kernel  2.6.16;  library  support  was
     added to glibc in version 2.4.
     renameat2() was added to Linux in kernel 3.15.

CONFORMING TO

     rename(): 4.3BSD, C89, C99, POSIX.1-2001, POSIX.1-2008.
     renameat(): POSIX.1-2008.
     renameat2() is Linux-specific.

NOTES

     Glibc  does not provide a wrapper for the renameat2() system call; call
     it using syscall(2).
 Glibc notes
     On older kernels where renameat() is  unavailable,  the  glibc  wrapper
     function  falls  back to the use of rename().  When oldpath and newpath
     are relative pathnames, glibc constructs pathnames based  on  the  sym-
     bolic  links  in  /proc/self/fd  that  correspond  to  the olddirfd and
     newdirfd arguments.

BUGS

     On NFS filesystems, you can not assume that if  the  operation  failed,
     the  file was not renamed.  If the server does the rename operation and
     then crashes, the retransmitted RPC which will be  processed  when  the
     server  is  up  again causes a failure.  The application is expected to
     deal with this.  See link(2) for a similar problem.

SEE ALSO

     mv(1), chmod(2), link(2),  symlink(2),  unlink(2),  path_resolution(7),
     symlink(7)

COLOPHON

     This  page  is  part of release 4.16 of the Linux man-pages project.  A
     description of the project, information about reporting bugs,  and  the
     latest     version     of     this    page,    can    be    found    at
     https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 RENAME(2)

/data/webs/external/dokuwiki/data/pages/man/renameat.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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